The present invention relates to an apparatus for measuring radiation angle dependence of scattered light, and particularly to apparatus capable of achieving very short time resolutions.
Apparatus is already known for measuring the angular dependence of light scattered from small particles, as described, for example, in J. Chem. Phys. 51, 1931 (1969). In this apparatus a laser beam is directed onto a narrow stream of particles at a constant angle and the angular dependence of the scattered radiation is measured with the aid of a detector fastened to an arm which is pivotal about the scattering volume. The measurement of this angular dependence then makes it possible to determine the size of the particles contained in the scattering volume.
Because, at the present day, the angular dependence of light scattered from small particles is to be recorded as a function of rapidly varying parameters or during very short time intervals, there is a need for a method which can take measurements in very short periods. With commercially available apparatus of the type described above the measurement of the angular dependence of the scattered light intensity of a suspension, for example, takes about 1 minute. For reasons of stability, the measurement time cannot be reduced by increasing the speed of rotation of the detector about the scattering volume by several orders of magnitude.
However, in many technical areas there is an increasing need for a much faster method, for example, for measuring short-time changes in the size of the droplets during formation of a fog, or the dependency of the cluster size upon inlet parameters, the monitoring of production in the manufacture of fibers, dies or colloids, testing of emulsification and coagulation processes, recording of the local and/or time variation in the size of aerosol particles in air, exhaust emission control for automobiles, examination of bacteria or rapid analysis of series thereof, analysis of the ejected matter in colloid drive mechanisms and measuring the change in size of plasma clusters. Particularly these last-mentioned measurements of changes in time require a method capable of making measurements in the nanosecond range.